1. Field of the Invention
The present invention relates to a mechanical press and more particularly to an auto-positioning inching control device for placing the slide in stop positions at various locations along the slide path.
2. Description of the Related Art
Mechanical presses of the type performing stamping and drawing operations employ a conventional construction which includes a frame structure having a crown and a bed and which supports the slide in a manner enabling reciprocating movement toward and away from the bed. These press machines are widely used for a variety of workpiece operations and employ a large selection of die sets with the press machine varying considerably in size and available tonnage depending upon its intended use.
A flywheel and clutch assembly are utilized to transmit mechanical energy from a main drive motor to the press crankshaft. The flywheel assembly serves as the primary source of stored mechanical energy and rotary driving power. Standard press configurations have the flywheel located between the main drive motor and clutch, with the flywheel being mounted on either the driveshaft, crankshaft or press frame by use of a quill. The main drive motor replenishes the flywheel with rotational energy as it becomes depleted due to press stamping operations during which the clutch engages the flywheel and establishes a driving connection between the flywheel and the crankshaft. When the crankshaft and flywheel are engaged in driving relationship, the flywheel energy is usefully converted into mechanical work to power the press components including the slide. During engagement of the clutch, the flywheel drops in speed as the press driven parts are brought up to running speed.
Setting the slide to a particular stroke position along the slide path is useful during tooling setup as well as stock material feed setup. Positioning the slide along the slide path can be accomplished by manually rotating the flywheel with the clutch engaged or by pulsing the clutch while the flywheel is rotating.
Manually rotating the flywheel may be accomplished by inserting a lever such as a long metal bar into bores within the flywheel. Lifting or pulling down on the bar will then manually rotate the flywheel and cause the slide to move up or down. This method of flywheel adjustment is time consuming and requires that flywheel motion be stopped. Slide positioning utilizing this method is inaccurate as it is based upon visual indication of slide position as perceived by the press operator.
Intermittently engaging or pulsing the clutch is additionally problematic as the frequent engagement and disengagement of the clutch causes excessive wear to the clutch components. Additionally, this method of slide adjustment produces inconsistent slide motion per pulse since the distance the slide moves per pulse is dependent upon, for example, counter balance settings and slide position. Since pulsing a clutch in equal time intervals will not produce equal slide movement, this method of achieving a stop position for the slide of a mechanical press is inaccurate as it is based upon visual indications of slide position as perceived by a press operator and unequal increments of slide movement.
What is needed in the art is a method and apparatus for allowing a press operator to choose preselected slide stop position zones in which the slide of a mechanical press may be stopped. What is further needed in the art is a device for placing the slide of a mechanical press into a preselected stop zone which does not require manual movement of the flywheel of the press, and which does not excessively wear the clutch and brake components of the press.
The present invention overcomes the disadvantages of the currently available methods and apparatus for placing the slide of a mechanical press in a particular stop zone along the slide path.
Generally, the present invention provides a mechanical press operator with a graphical user interface which can be utilized to select a preselected slide stop zone for the mechanical press slide. After selection of the slide stop zone, a computational device is utilized to compute the appropriate clutch dropout based upon press operational parameters such as slide speed, counter balance settings, slide position, and die characteristics. The computational device further monitors the computation time and adjusts clutch dropout accordingly. Since computation time is accounted for, processor speed does not affect the accuracy of the current invention.
The invention, in one form thereof, comprises a slide stop positioning device for positioning the slide of a mechanical press. The slide stop positioning device of this form of the current invention includes a slide actuator for moving the slide along the slide path and a selector which is operable to allow a press operator to select from a plurality of preselected slide stop zones. The selector is operatively connected to the slide actuator so that selection of one of the plurality of preselected slide stop zones will cause the slide actuator to position the slide accordingly. In one form of the current invention, the selector comprises a graphical user interface.
In one form of the current invention, the slide actuator includes a flywheel, a clutch and a crankshaft. The flywheel is rotatably supported by the press and is operable to receive and store rotational energy from a press drive motor. The clutch is operatively positioned for engagement with the flywheel and the crankshaft is operatively connected to the clutch and the slide so that rotational energy of the flywheel may be transmitted by the clutch and the crankshaft into reciprocating movement of the slide. The crankshaft has a top dead center position which corresponds to the rotational position of the crankshaft when the slide is furthest from the bed.
In one form of the current invention, the plurality of preselected slide stop zones comprise zones in 45 degree increments from the top dead center position. The graphical user interface may be, for example, a touch screen on which the plurality of slide stop zones may be arranged in circular form. Alternately, the user may predefine selected start/stop zones.
In one form of the current invention, a computational device is operative to compute a plurality of computed values including the necessary clutch dropout values for each of the plurality of preselected slide stop zones. The computational device may be, for example, a programmable logic controller or a microprocessor. Input means are communicatively connected to the computational device and are operable to communicate a plurality of input values to the computational device. The plurality of input values include a value of machine type, a value of counter balance settings, a value of slide position, a value of slide speed as well as values of die characteristics.
In one form of the current invention, the input means include a manually actuatable input device, a speed sensor, a slide position sensor and a counter balance position sensor. The manually actuatable input device is operative to input any of the plurality of input values. The speed sensor as well as the slide position and counter balance position sensors may be transducers of the type commonly utilized to monitor speed and position parameters. Additionally, RF tag or bar code readers may be utilized if RF or bar tag identifiers are utilized to store any of the plurality of input values. For example, RF tags or other communication devices, such as bar codes may be utilized to store information relating to die characteristics. Such communication of die characteristics is taught by pending U.S. patent application Ser. No. 09/062,210, the disclosure of which is herein explicitly incorporated by reference.
In one form of the current invention, the plurality of computed values computed by the computational device includes a value of computational device computation time for each computed clutch dropout value for each of the plurality of zones. A slide inching mechanism may be provided for use with the slide stop positioning device of the current invention. Such a slide inching mechanism will be operable to further adjust the slide position within any of the plurality of preselected slide stop zones. Such a slide inching mechanism is disclosed in U.S. Pat. No. 5,630,237, the disclosure of which is herein explicitly incorporated by reference.
The invention, in another form thereof, comprises a method of selecting a stop position for the slide of a mechanical press. The method of this form of the current invention includes the steps of: selecting one of a plurality of preselected slide stop zones, computing clutch dropout to achieve the selected preset stop zone for the slide, and disengaging the clutch as indicated by the computed clutch dropout.
In one form of the current invention, the step of selecting a stop zone for the slide further includes the steps of:
providing a graphical user interface including said plurality of preselected slide stop zones and selecting one of said plurality of preselected stop zones for the slide.
In one form of the current invention, the step of computing clutch dropout to achieve the selected preset stop zone for the slide further includes the steps of: providing a computational device, communicating a plurality of input values to said computational device, and computing clutch dropout using said computational device and said plurality of input values. Additionally, the step of providing a graphical user interface having a plurality of slide stop zones may comprise the step of: providing a touch screen having a plurality of selectable slide stop zones.
In one form of the current invention, the step of communicating a plurality of input values to the computational device further includes the steps of: communicating a value of machine type to said computational device, communicating a value of counter balance settings to said computational device, communicating a value of slide position to said computational device, communicating a value of slide speed to said computational device, and communicating values of die characteristics to said computational device.
In one form of the current invention, the method of selecting a stop position for the slide of a mechanical press further includes the step of: providing a slide inching mechanism for further adjusting slide position after the slide comes to rest in a preselected slide stop zone. In yet another form of the current invention, the method of selecting the stop position for the slide of a mechanical press further includes the steps of: monitoring computation time for said computational device and adjusting the value of clutch dropout to account for the monitored computation time.
An advantage of the present invention is the ability to stop the slide of a mechanical press in multiple positions along the slide path without manually rotating the flywheel.
Another advantage of the present invention is the ability to position the slide of a mechanical press at various stop positions along the slide path without causing excessive wear to the clutch and brake components of the press.
A further advantage of the present invention is the ability to position the slide of a mechanical press at differing stop positions along the slide path without relying upon the perception of the press operator to position the slide at a particular location.